What Animal Do Humans Share The Most Dna With

News Release 11-025

The Most Genes in an Animal? Tiny Crustacean Holds the Record

New "model organism" to help environmental health protection

February 3, 2011

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Scientists have discovered that the beast with the almost genes--about 31,000--is the near-microscopic freshwater crustacean Daphnia pulex, or water flea.

By comparison, humans have almost 23,000 genes. Daphnia is the first crustacean to accept its genome sequenced.

The water flea's genome is described in a Science paper published this week by members of the Daphnia Genomics Consortium, an international network of scientists led by the Center for Genomics and Bioinformatics (CGB) at Indiana Academy (IU) Bloomington and the U.Southward. Department of Energy's Joint Genome Constitute.

"Daphnia's high gene number is largely because its genes are multiplying, creating copies at a college rate than other species," said project leader and CGB genomics director John Colbourne.

"Nosotros gauge a rate that is three times greater than those of other invertebrates and thirty percent greater than that of humans."

"This analysis of the Daphnia genome significantly advances our understanding of how an organism'due south genome interacts with its environs both to influence genome structure and to confer ecological and evolutionary success," says Saran Twombly, program director in the National Science Foundation (NSF)'s Segmentation of Environmental Biology, which funded the research.

"This gene-environment interplay has, to date, been studied in model organisms under artificial, laboratory conditions," says Twombly.

"Because the ecology of Daphnia pulex is well-known, and the organism occurs abundantly in the wild, this analysis provides unprecedented insights into the feedback between genes and environment in a real and always-changing environment."

Daphnia's genome is no ordinary genome.

What reasons might Daphnia have so many genes compared to other animals?

A possibility, Colbourne said, is that "since the majority of duplicated and unknown genes are sensitive to environmental conditions, their accumulation in the genome could business relationship for Daphnia's flexible responses to environmental modify."

Scientists take studied Daphnia for centuries because of its importance in aquatic food webs and for its transformational responses to ecology stress.

Similar the virgin nymph of Greek mythology that shares its name, Daphnia thrives in the absence of males--by clonal reproduction, until harsh environmental weather favor the benefits of sex.

"More one-tertiary of Daphnia's genes are undocumented in any other organism--in other words, they are completely new to scientific discipline," says Don Gilbert, paper co-author and scientist at IU Bloomington.

Sequenced genomes oft contain some fraction of genes with unknown functions, even among the well-nigh well-studied genetic model species for biomedical research, such every bit the fruit wing Drosophila.

By using microarrays (containing millions of Dna strands affixed to microscope slides), experiments that subjected Daphnia to ecology stressors point to these unknown genes having ecologically significant functions.

"If such big fractions of genomes evolved to cope with environmental challenges, information from traditional model species used but in laboratory studies may be insufficient to discover the roles for a considerable number of animal genes," Colbourne said.

Daphnia is emerging equally a model organism for a new field of science--ecology genomics--that aims to meliorate understand how the environment and genes interact.

This includes a practical need to employ scientific developments from this field to managing our water resources and protecting human being wellness from chemical pollutants in the environs.

James Klaunig, a scientist at IU Bloomington, predicts that the work will yield a more than realistic and scientifically-based risk evaluation.

"Genome research on the responses of animals to stress has of import implications for assessing environmental risks to humans," Klaunig said. "Daphnia is an exquisite aquatic sensor, a potential high-tech and modern version of the mineshaft canary."

"With knowledge of its genome, and using both field sampling and laboratory studies, the possible effects of environmental agents on cellular and molecular processes can exist resolved and linked to similar processes in humans."

The scientists learned that of all sequenced invertebrate genomes so far, Daphnia shares the virtually genes with humans.

Daphnia's gene expression patterns change depending on its environment, and the patterns bespeak what state its cells are in.

A water flea bobbing in water containing a chemic pollutant will tune-up or tune-downwards a suite of genes differently than its sisters accepted to water without the pollutant, for example.

The health furnishings of most industrially produced compounds in the surroundings are unknown, because current testing procedures are likewise slow, also plush, and unable to indicate the causes for their effects on animals, including humans.

Over the grade of the project, the Daphnia Genomics Consortium has grown from a scattering of founding members to more 450 investigators around the globe.

"Assembling and so many experts around a shared enquiry goal is no small-scale feat," said Peter Cherbas, director of the CGB. "The genome project signals the coming-of-age of Daphnia as a research tool for investigating the molecular underpinnings of key ecological and environmental problems."

Colbourne agreed, adding, "New model systems rarely get in on the scene with such articulate and important roles to play in advancing a new field of science."

The work besides received support from the U.Southward. Department of Free energy, Lilly Endowment Inc., Roche NimbleGen Inc., the U.S. National Institutes of Health, the U.S. Department of Health and Homo Services, and Indiana University.

-NSF-

Daphnia, or water flea, with a clonal breed of offspring.
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A defensive helmet helps protect Daphnia confronting predators.
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Daphnia with mild defensive neckteeth; the teeth are used against predators.
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Juvenile Daphnia with and without defensive neckteeth.
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The researchers' findings are described in the Feb. four, 2011 issue of the journal Science.
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Media Contacts
Cheryl Dybas, NSF, (703) 292-7734, electronic mail: cdybas@nsf.gov
David Bricker, Indiana University, (812) 856-9035, email: brickerd@indiana.edu

Related Websites
Daphnia Genome Consortium: http://daphnia.cgb.indiana.edu

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